JPS6298570A - Electrode substrate for end seal-mounting fuel cell and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an electrode substrate, effective for phosphoric acid type fuel cell, having good phosphoric acid resistance by joining an electrode and a separator with a flexible graphite sheet, and an end sealing part and the separator with a fluorine resin. CONSTITUTION:An electrode substrate consists of two electrodes 1 each of which has reaction gas passages 6, a separator 2 placed between two electrodes, and end seals 3 installed at the ends vertical to the reaction gas passages 6 in the electrodes. A flexible graphite sheet 4 is interposed between the separator and the electrode 1. The extended periphery of the separator and the end seal 3 are joined through fluorine resin 5. The electrode substrate for end seal- mounting fuel cell is manufactured in such a way that a flexible graphite sheet is interposed between the electrode and the separator, and they are joined through adhesive and baked at about 1,000 deg.C or higher. The extended periphery of the separator from the periphery of the electrode and the end seal are joined through fluorine resin sheet or dispersion.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention generally relates to an electrode substrate for a phosphoric acid fuel cell,
More specifically, a porous carbonaceous electrode portion provided with a reactive gas flow path is joined to both sides of a separator via a flexible graphite sheet such that the reaction gas flow path is orthogonal to each other and faces each other, and A pair of end seal parts are arranged adjacent to the peripheral edge of the electrode part parallel to the reaction gas flow path, and this end seal part made of a gas-impermeable dense carbon material is connected to the fluororesin electrode. Related to the board.

In the electrode substrate for a fuel cell with an end seal portion of the present invention, the separator and the electrode portion are bonded via a flexible graphite sheet and fired to form a carbon body, and the end seal portion and the separator are bonded to each other via a flexible graphite sheet. Since it is bonded with fluororesin, it has particularly excellent phosphoric acid resistance, and the edge sealing material is evenly arranged and bonded on both sides with a separator in between, which has a reinforcing effect. Therefore, it has excellent handling properties.

[Prior Art 1] In general, substrates serving as electrodes in phosphoric acid fuel cells are stacked with one side in contact with a phosphoric acid matrix and the other side in contact with a separator.

Furthermore, when stacking electrode substrates to form a fuel cell, a sealing material is placed at the ends of the electrode substrates to prevent reaction gas from diffusing to the outside from the side surfaces of the cell electrode substrates.

In such fuel cells, carbon cement has conventionally been used to join each member.

However, because carbon cement is oxidized by phosphoric acid, there is a possibility that parts may peel apart or that reactive gases may leak through the joints.

Furthermore, since the electrode substrate is usually in the form of a thin plate, there is a problem in terms of mechanical strength that it may break during handling, especially if the substrate area is large.

[Problem of the Invention] An object of the present invention is to provide an electrode substrate for a fuel cell with an end seal part, in which a peripheral gas seal part is joined to a separator.

Another object of the present invention is to provide an electrode substrate for a phosphoric acid fuel cell that has excellent resistance to phosphoric acid.

Further objects and advantages of the present invention will be apparent to those skilled in the art from the following description.

[Structure of the Invention] The present invention is characterized in that a porous carbonaceous electrode portion provided with a reactive gas flow path is joined to both sides of a separator via a flexible graphite sheet such that the reactive gas flow paths are orthogonal to each other and face each other. and adjacent to the peripheral edge of the electrode part parallel to the reaction gas flow path, a pair of end seal parts made of a gas-impermeable dense carbon material are joined to the separator via a fluororesin layer. The present invention provides an electrode substrate for a fuel cell having an end seal portion A.1 and a method for manufacturing the same.

[Detailed Description] Hereinafter, the electrode substrate of the present invention will be described in more detail with reference to the accompanying drawings.

The figure is a perspective view of the electrode substrate of the present invention. The figures are exaggerated and do not necessarily represent the actual size. Suitable dimensions for each member, particularly with respect to thickness, will be apparent to those skilled in the art.

The electrode substrate of the present invention includes two electrode sections 1 having reactive gas channels 6, a separator 2 located between the two electrode sections, and an end portion of the electrode sections perpendicular to the reactive gas channels 6. It has a structure consisting of an end seal portion 3.

The separator 2 is larger than the electrode section 1, and extends outward from the periphery of one electrode section along the edge parallel to the reaction gas flow path G of one electrode section as shown in the figure. the outer end of which coincides with the outer end of the other electrode part), and an end seal part 3 is joined to this extension part. Separator 2
A flexible graphite sheet 4 is interposed between the electrode section 1 and the separator periphery'Il end extending outward and the end seal section 3 are respectively joined via a fluororesin 5. There is.

The electrode part is made of porous carbonaceous material, with an average bulk density of 0.3 to 0.9 g/cc under firing strain at 1000°C or higher.
Gas permeability 200mf! / ci-hr ・mmA
It is preferable to have characteristics of q or more and electrical resistance of 200 mΩ·cm or less.

The separator has an average bulk density of 1.4a/cc or more and a gas permeability of 10-6m/ci/hr -111111A
Q or less, electrical resistance of 10 mΩ·cm or less, and thickness of 2 JD or less are preferable.

The above-mentioned end seal part has an average bulk density of 1.4 g/cc or more and a gas permeability of 10"'mf! / ci · hr -
It is preferably 111 mA q or less.

As already mentioned, in the fuel cell electrical board of the present invention, all end seals and separators are joined via fluororesin. Diffusion is dominant along the leakage line and is not affected much by pressure, but the present invention
Under the differential pressure of A and Q, the leakage gas per unit time per peripheral length of the joint is expressed by the relationship [leak gas claw/edge length]/(differential pressure): 10'mi2/cs
-hr-mmAq or less is preferable.

The fluororesin used in the present invention is generally a fluororesin with a melting point of 200°C or higher, and is not particularly limited.
27℃, 4.6Kgf/cffl heat distortion temperature 121℃)
, tetrafluoroethylene-hexafluoropropylene copolymer resin (
Abbreviation: FEP, melting point: 250-280°C.

4.6 g f / ci heat distortion temperature 72℃), fluorinated aluminum]oxyethylene resin (abbreviation PF△, melting point 300-3
10℃.

4.6Kgf/Cff1 heat distortion temperature 75℃), fluorinated ethylene propylene resin (abbreviation TFP, melting point 290-30
0℃). These fluororesins are commercially available.

In the present invention, the fluororesin has a thickness of, for example, 50 mm.
It is used as a sheet of about μ or a dispersion of about 60% by weight. Small amounts of surfactants can be added to this dispersion.

To manufacture the fuel cell electrical plate 141 with end seals of the present invention, a flexible graphite sheet is sandwiched between the electrode member and the separator material, and both sides of the sheet are bonded together with an adhesive. It is further fired at about 1,000°C or higher, and then the extended portion of the leverator material extending outward from the periphery of the electrode part and the end sealing member are interposed with a fluororesin sheet or dispersion. Join.

The following are used as the electrode members of the electrode substrate of the present invention.

■ Molded mixture of short flame fibers, binder and granular material under heat and pressure (for example, Japanese Patent Application Laid-Open No. 59-6817)
(See No. 0). In particular, short carbon fibers with a length of 2 mm or less 20 to 6
0 wt%, 20 to 50 wt% of phenolic resin, and 20 to 50 wt% of organic particulate matter (pore control material) at a molding temperature of 100 to 180°C and a molding pressure of 2 to 100 (Jf/ci, pressure holding time of 1 to 100%). Molded for 60 minutes.

(2) The molded member of [1] above is fired at 1,000°C or higher.

■ Mixed paper made by mixing carbon fibers with a length of 20111111 or less and at least one organic fiber selected from valves, regenerated cellulose m fibers, polyacrylonitrile fibers, etc., with a papermaking binder (polyvinyl alcohol fibers, etc.). A molded article in which a gas diffusion part is made of paper impregnated with a solution of phenolic resin (for example, see Japanese Patent Publication No. 18603/1983), and a rib part is formed using the raw material described in [1].

■ The molded product of [3] above is fired at 1,000°C or higher.

The separator material used in the present invention is 2.000℃
A dense carbon plate having a firing shrinkage rate of 0.2% or less when fired at is preferable.

The flexible graphite sheet made by compressing expanded graphite particles used in the present invention has a particle size of 5IllI! It is made by compressing expanded graphite particles obtained by acid treatment and further heating of graphite particles of 1 mm or less, and has a thickness of 1 mm or less and a bulk density of 1.0 to 1.
．． 5 (1/CC, compressive strain rate (i.e., compressive load 1
'Jf/cIli distortion factor) is 0.35x 10
-2rffl/gr or less, and the radius of curvature is 20mm
It is preferable to use a flexible material that does not break even when bent up to a maximum of UCC. ! I-Graphoil ■ is a suitable example.

The enclosing agent used on each joint surface when joining the above electrode member and separator material via a flexible graphite sheet may be an adhesive normally used for adhering carbon materials, but in particular, phenol resin , epoxy resin, furan resin, etc.: Thermosetting resin C is preferably selected.

The thickness of this adhesive layer is not particularly limited, but
Generally, it is preferable to uniformly apply the coating to a thickness of 0.5 mm or less.

In addition, the adhesive bonding is performed at a temperature of 100° to 180°.
℃, press pressure 1.5 to 50 gf/Cff1. Pressing can be carried out within a range of 1 to 120 minutes.

After the electrode member is bonded to the separator material via the flexible graphite sheet as described above, it is fired at a temperature of about 1,000°C or higher.

Thereafter, a fluororesin sheet or dispersion is sandwiched between the elongated part of the separator material and the surface of the end sealing member joined thereto, and Iζ is applied, and 2K (lf/
Fusion bonding is performed at a pressure of cff1 or more and a temperature of (melting point -50°C) or more of the resin.

As the end sealing member, a dense carbon material having a firing shrinkage rate of 0.2% or less when fired at 2,000°C is preferable.

[Effect of the invention] The end seal part combustion F of the present invention obtained as described above
Since the end seal part of the battery electrode plate is integrally bonded, it is not necessary to provide a peripheral seal member to prevent leakage of reactant gas to the side of the cell, which is required in normal fuel cells. Not only is Moraron 2 unnecessary, but it also has the following effects.

In other words, the electrode part and the lever are made of flexible graphite sheets, and the end seal part and the separator are made of fluororesin, so they have excellent phosphoric acid resistance and can be used as electrode substrates for phosphoric acid fuel cells. Particularly useful. In addition, the end seals are evenly arranged and bonded around the flaky electrode substrate, intersecting on both sides with a separator in between, which has a reinforcing effect, and as a result, when manufacturing fuel cells, etc. Excellent handling properties.

[Implementation (I111)] Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to the following Examples. Manufactured by Kogyo Co., Ltd., product name IVl-2
048, average diameter 141J! R1 average length 4007m)
35 wt%, phenol resin (Asahi Uisozai Co., Ltd., Jyo, trade name RM-210), 30 wt%, and polyvinyl alcohol particles (manufactured by Nippon Gosei Kagaku Co., Ltd., average particle size 1801
iIn) After mixing 35wt%, supply it to a predetermined mold,
The molding temperature was 135°C, the molding pressure was 35, Q f / cm, and the pressure nozzle was held for 20 minutes.
Vertical) x720mm, (E 7J) Xl, 5m
A ribbed electrode member having a size of m (thickness) was manufactured. The rib part is 1.0mm, and the gas diffusion part is 065111m.

■ Separator material Showa Denko Co., Ltd.'s dense carbon plate (thickness 0.8 mm) is used vertically.
It was cut to 720 mm horizontally and used as a separator material.

■ End sealing material A dense carbon plate manufactured by Tokai Carbon Co., Ltd. (bulk density 1, 85 g/cc, thickness 1.5 n+m) is 60 mm long x 72 mm wide.
It was cut into pieces of 0 mm (4 pieces) to obtain end seal members.

■ Teflon ■ Teflon sheet (thickness o, 05mm, Nichias Co., Ltd.)
(manufactured by) is used.

■Flexible graphite sheet Graphoil ■ (manufactured by IJcc, bulk density 1.101/cc, thickness 0.13 mm) was cut appropriately according to the dimensions of the joint surface and used at °C.

After applying phenolic resin adhesive on both sides of the above lobarator material and one side of graph oil, it was dried. Thereafter, bonding was carried out at 135° C. and 10 g f / (:ti) for 20 minutes.

Next, the above adhesive was applied to the graph oil surface of the L-arranged joint and dried. Similarly, the adhesive was applied to the rib portion surface of the electrode member and dried. Its temperature is 135℃ 110K (
Jf/cA, bonded for 20 minutes, then 2,000
It was fired at 0°C.

Next, 1-
A Noron sheet was held in between. Then 360℃.

Melt pressure bonding was performed at 20 KOf/cffl.

In order to measure the peel strength of the melt-pressed surface, the test piece was adhered to a measuring jig with an epoxy adhesive and a tensile test was conducted. The peel strength was estimated to be 90 Kgf/cm or more since the epoxy adhesive was peeled off at the joint between the Teflon sheets. This peel strength of 90Kq 170111 or more is actually 30 times the peel strength of 3Kgf/CrA when bonding ordinary carbon material plates with a thermosetting resin solution adhesive.

Instead of the deflon sheet in Example 1, use Teflon dispersion (Mitsui Flo [1 Chemical L)'ffl.

Aqueous solution containing 60% by weight (abbreviated as PTFE) was applied evenly to the joint surface of the end sealing member and the separator material, and dried in air. After that, 360℃.

20 g f / cr? It was melted and pressed at r.

The peel strength was the same as in Example 1.

[Brief explanation of drawings]

The attached figure is a perspective view of the electrode substrate of the present invention. 1... Electrode part, 2... Separator,
3...End seal portion, 4...Flexible graphite sheet, 5...Fluororesin, 6...
Reactant gas flow path.

Claims (17)

[Claims] (1) A porous carbonaceous electrode portion equipped with a reactive gas flow path is joined to both sides of the separator via a flexible graphite sheet so that the reaction gas flow path is orthogonal to each other and faces each other, and 1 adjacent to the peripheral edge parallel to the reaction gas flow path of the electrode part.
1. An electrode substrate for a fuel cell with an end seal portion, characterized in that a pair of end seal portions are arranged, and the end seal portion is joined to an extended portion of the separator via a fluororesin layer. (2) When the porous carbonaceous electrode part is fired at 1,000°C or higher, the bulk density is 0.3 to 0.9 g/cc, 200
The fuel cell electrode substrate with an end seal portion according to claim 1, which has a gas permeability of ml/cm^2.hr.mmAq or more and an electrical resistance of 200 mΩ.cm or less. . (3) Separator has a bulk density of 1.4 g/cc or more, 1
Gas permeability of 0^-^6ml/cm^2・hr・mmAq or less, electrical resistance of 10mΩ・cm or less, and 2mm
The electrode substrate for a fuel cell with an end seal portion according to claim 1 or 2, which has a thickness as follows. (4) Claim 1, characterized in that the end seal portion has a bulk density of 1.4 g/cc or more and a gas permeability of 10^-^4ml/cm^2.hr.mmAq or less. The electrode substrate for a fuel cell with an end seal portion according to any one of items 1 to 3. (5) Claim 1, characterized in that the flexible graphite sheet is produced by compressing expanded graphite particles.
4. A fuel cell electrode substrate with an end seal portion according to any one of items 1 to 4. (6) The flexible graphite sheet is manufactured by compressing expanded graphite particles obtained by acid-treating graphite particles with a particle size of 5 mm or less and further heating, and has a thickness of 1 mm or less and a bulk density of is 1
．． 0~1.5g/cc, compressive strain rate 0.35×10^-
^2cm^2/Kgf or less, and the radius of curvature is 20mm
The electrode substrate for a fuel cell with an end seal portion according to claim 5, characterized in that it has such flexibility that it will not break even if it is bent to a certain extent. (7) The electrode substrate for a fuel cell with an end seal portion according to any one of claims 1 to 6, wherein the fluororesin has a melting point of 200°C or higher. (8) A porous carbonaceous electrode member provided with reaction gas passages on both sides of the separator material is arranged so that the reaction gas passages are perpendicular to each other and face each other, and between the electrode member and the separator material. After bonding with an adhesive with a flexible graphite sheet interposed between the electrodes and firing at a temperature of about 1,000°C or higher to produce a fuel cell electrode substrate, a pair of electrodes parallel to the reactant gas flow paths perpendicular to each other are bonded. An end portion made of a gas-impermeable dense carbon material with a fluororesin sheet or dispersion interposed between the extended portion of the separator material adjacent to the peripheral end portion of the electrode member and extending outward from the peripheral edge of the electrode portion. A method for manufacturing a fuel cell electrode substrate with an end seal portion according to claim 1, which comprises joining a seal member. (9) A porous carbonaceous electrode member, [1] A molded member obtained by integrally molding a mixture of short carbon fibers, a binder, and an organic particulate material under heat and pressure, [2] A molded member obtained by firing the molded member of [1] above. [3] Phenol is added to the mixed paper obtained by mixing carbon fiber and at least one organic fiber selected from pulp, regenerated cellulose fiber, and polyacrylonitrile fiber together with a papermaking binder (polyvinyl alcohol fiber, etc.). The gas diffusion section is made of paper impregnated with a resin solution, and the [
9. The method according to claim 8, wherein the molded member is selected from a molded member in which a rib portion is formed from the mixture of [1] and [4] a fired member in which the molded member in [3] is fired. (10) The separator material is a dense carbon plate having a firing shrinkage rate of 0.2% or less when fired at 2,000°C. Method. (11) Claim 8, characterized in that the flexible graphite sheet is produced by compressing expanded graphite particles.
The method according to any one of Items 1 to 10. (12) The flexible graphite sheet is manufactured by compressing expanded graphite particles obtained by acid-treating graphite particles with a particle size of 5 mm or less and heating them, and has a thickness of 1 mm or less and a bulk density of 1
．． 0~1.5g/cc, compressive strain rate 0.35×10^-
^2cm^2/Kgf or less, and the radius of curvature is 20mm
12. The method according to claim 11, wherein the method has such flexibility that it does not break even when bent. (13) Any one of claims 8 to 12, wherein the adhesive for the flexible graphite sheet is a thermosetting resin selected from phenol resin, epoxy resin, and furan resin. The method described in. (14) The bonding conditions between the electrode member and the separator material are a temperature of 100 to 180°C and a press pressure of 1.5 to 50 Kgf/c.
14. The method according to any one of claims 8 to 13, characterized in that the pressing time is in the range of 1 to 120 minutes. (15) The end sealing member is a dense carbon material having a firing shrinkage rate of 0.2% or less when fired at 2,000°C. Any method described. (16) The method according to any one of claims 8 to 15, wherein the fluororesin has a melting point of 200°C or higher. (17) The joining conditions of the end seal member are 2 kgf/
cm^2 or more, and the temperature is at least (melting point -50°C) of the fluororesin (melting point -50°C) or more
The method according to any of paragraph 16.